Immunotoxin depletion of T cells and its effect on hematopoietic progenitor cells in human cord blood

Objective To study the selective toxicity of immunotoxin (IT) on T cells in cord blood and simultaneously determine its effect on hematopoietic progen itor cells. Methods The percentage of CD5 and CD8 T cell subsets in cord blood (CB) and bone marrow (BM) as well as peripheral blood (PB) was measured by immunoen zymatic labeling of monoclonal antibodies using immune complexes of alkalin e phosphatase and monoclonal anti-alkaline phosphatase (APAAP complexes). O ne-way mixed lymphocyte cultures (MLC) were performed to compare the prolif erative response of CB with that of PB. The proliferative capability of cor d blood T cells and T lymphocyte transformation capacity were evaluated in the presence of anti-CD8 or anti-CD5 immunotoxin by one-way MLC and colorim etric MTT (tetrazolium) assay, respectively. The effect of IT on the growth of hematopoietic progenitor cell of colony forming unit-granulocyte and ma crophage (CFU-GM), burst forming unit-erythroid (BFU-E), multipotential hem otapoietic progenitors (CFU-Mix) from CB were estimated by colony-forming a ssays. Results A certain proportion of CD5 and CD8 T cells existed in CB. The allo proliferative capacity of CB was similar to that of PB. CD5: Ricin at a dos age of 1 x 10(-10) - 1 x 10(-8) mmol/L and CD8: Ricin concentration in the range of 1 x 10(-9) -1 x 10(-8) mmol/L effectively decreased both the proli ferative capability of T cells in MLC during CB and T cell transformation. Over the dosage of 1 x 10(-10) - 1 x 10(-9) mmol/L, both kinds of IT didn't obviously affect the growth of hematopoietic progenitor cells. Conclusion CD5: Ricin and CD8: Ricin may effectively deplete T cells and ma y not significantly inhibit the function of hemaptopoietic cells at a speci fic dosage.